Transcript chapt19_image

Chapter 19
Systematics and
Phylogency
• Systematics reconstructs evoluntary history and
classifies or groups organisms according to
evolutionary findings
• An organized approach using data from fossil record,
comparative anatomy, and molecular data to
determine evolutionary relationships
• Taxonomy is the branch of biology that identifies,
names, and classifies organisms
• A natural system of classification is based on the
understanding of how organisms are related to each
other through evolution
• Greek philosopher, Aristotle, identified organisms and
put them in groups
• In Middle Ages, names were changed to Latin
descriptions
• John Ray in seventeenth century shortened many of
the descriptions
Fig. 19.2
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
b. Lilium canadense
a.
c. Lilium bulbiferum
a: Courtesy Uppsala University Library, Sweden; b: © Arthur Gurmankin/Visuals Unlimited; c: © Dick Poe/Visuals Unlimited
• Mid-eighteenth century, Carlolus Linnaeus developed
binomial nomenclature
• Each species has a two-part name
• First word is genus, a classification category that
contains related species
• Second word is the specific epithet that sometimes
tells us something descriptive about the organism
• Scientific name is in italics (or underlined if
handwritten)
• Genus is capitalized and specific epithet is not
• Genus name can be used alone if referring to a group
of organisms
• Genus can be abbreviated to a single letter if used
with specific epithet and if full name has been given
before
• Homo sapiens is the scientific name for modern
humans
• Common names often vary from place to place
• Sometimes the same common name may indicate
different organisms in different places
• Latin was the universal language at the time of
Linnaeus and scholarly work appeared in the Latin
• Scientists throughout the world use the same scientific
binomial name
• The Linnaean Society rules on the appropriateness of
the binomial name for each species
• Today about a million species of animals and a half
million species of plants and microorganisms have
been named
• All birds have been named, but numerous insects
remain to be named
Fig. 19.3
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
DOMAINS
KINGDOMS
PHYLA
CLASSES
ORDERS
Eukarya
FAMILIES
Plantae
Anthophyta
GENERA
Eudicotyledones
Vitales
Vitaceae
SPECIES
Parthenocissus
P. quinquefolia
Parthenocissus quinquefolia
Virginia creeper (five-leaf ivy)
• A taxon is a group of organisms that fills a particular
category of classification
• Linnaeus published his work on classification in
Systema Naturae in 1735
• Today, taxonomists used these major categories of
classification: species, genus, family, order, class,
phylum, kingdom, and domain
• The higher the category, the more inclusive it is
• Categories are nested because one group exists inside
another group
• Ex. Domain contains many kingdoms and one
kingdom contains many phyla etc.
• Traits shared by organisms in a classification category
are called characters
• Aim of systemics is to determine phylogeny
• A depiction of evolutionary history is a phylogentic
tree
• The tree has many branch points and they show that it
is possible to trace the ancestry of a group of
organisms back farther and farther in past
Page 341
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
reindeer
monkeys
apes
common ancestor
(placental mammal)
• Because classification is hierarchical, classification
categories can be used to construct a phylogenetic tree
• A species is more closely related to other species in
the same genus and is related to, but less so, to genera
in the same family
Fig. 19.4
Order
Family
Genus
Species
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
Aepyceros
Melampus
(impala)
Oryx
gazella
(oryx)
Aepyceros
Oryx
Cervus
elaphus
(red deer)
Rangifer
tarandus
(reindeer)
Cervus
Rangifer
Bovidae
Cervidae
Artiodactyla
• Cladistics is based on the work of Willi Hennig
• A way to trace evolutionary history of a group by
using shared traits, derived from a common ancestor,
to determine which species are most closely related
• These traits are used to construct phylogenetic trees
called cladograms
• Cladogram is the evolutionary history of a group
based on the available data
• Begins with a table that summarizes the derived traits
of the species being compared
• At least one (or more) species is considered an
outgroup
• Any trait found in both the ingroup and outgroup is a
shared ancestral trait that has been present in a
common ancestor
• An outgroup shows which traits are shared derived
traits called synapomorphies
• Any trait not found in outgroup is a shared derived
trait
• We can use fossil record to discover which traits are
shared traits, but fossil record is rarely complete
• All synapomorphies indicate evolutionary
relationships among members of ingroup that are used
to construct the cladogram
• A cladogram contains several clades
• Each clade includes a common ancestor and all its
descendants that share one or more synapomorphies
• Difference in synapomorphies distinguish clades
Fig. 19.5
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
mammary glands
hair
gizzard
Traits
epidermal scales
amniotic egg
four limbs
vertebrae
notochord in
embryo
tuna
frog
lizard
crocodile
finch
dog
chimpanzee
ingroup
lancelet (outgroup)
Species
• Cladogram is objective because it lists the data used
• Usually uses many traits
• A cladogram is a hypothesis that can be tested and
either corroborated or refuted with new data
Fig. 19.6
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
enlarged brain
common ancestor
hair, mammary glands
Amniotic
egg
chimpanzee
long canine teeth
terrier
feathers
gizzard
four limbs
finch
crocodile
epidermal
scales
lizard
vertebrae
frog
common
ancestor
tuna
lancelet (outgroup)
• Cladists use the principle of parsimony, which states
that the minimum number of assumptions is the most
logical
• Cladograms are constructed to leave the fewest
number of shared derived characters unexplained or
that minimizes the number of evolutionary changes
• Parsimony problems arise when DNA sequencing is
used to make cladograms
• Mutations, especially in noncoding DNA, can be high
so base changes are not reliable data to distinguish
clades
• Because of this, some systematists use statistical tools
not parsimony to build phylogenetic trees
• This branch of systematics is called statistical
phylogenetics
• Clades are often nested inside other clades
• From the cladogram we looked at, birds are closely
related to crocodiles and should be classified with
them as well as with lizards
Page 344
• Birds, dinosaurs, lizards, snakes, and crocodilians can
trace ancestry to amniotes called diapsids
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
dorsal temporal
opening
lateral temporal
opening
• They have the skull openings of a diapsid
orbit
• Cladistics only allow monophyletic groupings
• A monophyletic group includes a common ancestor
and all the descendants of that ancestor
• A paraphyletic group contains a common ancestor and
does not include all the descendants
• A polyphyletic group contains some of the
descendants of more than one common ancestor and
not all the common ancestors
• Because Linnean classification system allows
groupings other than monophyletic, biologists are
presently trying to determine how it could be changed
to reflect our current understanding of phylogeny
• Homology is structural similarity that stems from
having a common ancestor
• Homologous structures are similar to each other
because of common descent
• Convergent evolution has occurred when distantly
related species have a structure that looks the same
only because of adaptation to the same type of
environment
• Analogy is similarity due to convergence
• Analogous structures have the same function in
different groups, but do not have a common ancestry
• Evidence exists that dinosaurs cared for their young in
a manner similar to crocodilians and birds
• Behavioral and morphological data indicates that
dinosaurs, crocodilians, and birds are related through
evolution
• Cytochrome c is a protein that is found in all aerobic
organisms, and its sequence has been determined for a
number of different organisms
• The amino acid differences indicate how closely
related organisms are
• Study of RNA differences between prokaryotes and
eukaryotes resulted in the acceptance of the threedomain system of classification
• DNA differences can substantiate data, help trace the
course of macroevolution, and fill gap in fossil record
Fig. 19.10
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
• Molecular clocks
data to suggest
have been
human
common
chimpanzee
white-handed
gibbon
rhesus
monkey
green
monkey
capuchin
monkey
60
50
40
30
20
Million years ago (MYA)
10
Increased difference in DNA
PRESENT
use DNA sequence
how long primates
separate
• From Aristotle to twentieth century, biologists used
two kingdoms: kingdom Plantae and kingdom
Animalia
• In 1880s, Ernst Haeckel proposed a third kingdom
called Protista
• In 1969, R.H, Whittaker expanded the classification
system to five kingdoms: Monera, Protista, Fungi,
Plantae, and Animalia
• In late 1970s, Carl Woese using RNA data proposed
two groups of prokaryotes the bacteria and the
archaea
• They are so different that they are raised to a higher
category called a domain
• Now we use a three domain system
• Domain Bacteria is a large diverse group found nearly
everywhere on Earth
• Domain Archaea that look like bacteria, but are
different in their rRNA base sequences and unique
plasma membranes and cell wall chemistry
• Domain Eukarya are unicellular to multicellular
organisms whose cells have a membrane-bound
nucleus and various organelles
Fig. 19.11
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
fungi
plants
EUKARYA
protists
protists
heterotrophic
bacteria
cyanobacteria
BACTERIA
ARCHAEA
common ancestor
animals